roof top tents and antennas.....

[serrasalmus]

first a lil info on the 95 Grand Cherokee ive lovingly dubbed grandpa he's old and full of piss and vinegar, although he does leak a lil, at 235k on the soul hes a go getter that loves to show where experience and a steady foot (a good set of tires helps too...)can take you 

 

so grandpas carrying the smittybuilt overlander xl rooftop tent....its huge takes up almost all of the roof. tent is 75x47 and is 15inches from the roof, by almost, i got about 10 inchs to use and most of that is the roof line bending down. the tent base is mainly fiberglass bottom sections with what i would call angle iron but its aluminum. then in the center of it sits a aluminum ladder. now on the rear left fender i have a 102" (cant beat'em for there indestructability) for the cb and the tent absolutely destroys swrs I'm lucky to get 2.5 and my range is cut drastically and the antenna is still 75% above the tent line. right now I've got a (i know its not the best) Nagoya ut72 mag mount. running 1.02to 1.03 swr on the roof in the small space as far away from the tent as it can be. ive also tried on the hood close to where your stock stereo antenna would be(cut mine off it got beat to death by Colorado mtn trees anyway) but on the hood, the swrs there i got to a flat 1.0 thru the band. all doors, hood, and hatch have been bonded with 1/2 tinned copper ground straps that are no longer then 6 inches if i could help it

 

 is the tent going to kill the signal on the 70cm band as it does on the 11m band. id like todo a nmo roof mount with a 5/8 over 5/8 to get the extra height. the tent actually moves a lot of the branches before they get to the antenna. the other option is a nmo fender mount but that's going to get beat to hell and back i feel. so that leaves the hood option for a mag mount as im not sure id like to mount a nmo in the hood (wouldn't there be a ton of surrounding rfi). 

 

so I'm trying to decide which route would be the best for my situation and wanted to get yalls opinions and thoughts. 

 

 

[SkylinesSuck]

I've got no input, but would like to see a zoomed out pic of your GC! Jeep porn ftw

[serrasalmus]

ill figure out how to get some with links soo i dont use up my 500kb of uploads on non radio related items.

 

I've got no input, but would like to see a zoomed out pic of your GC! Jeep porn ftw

[axorlov]

Before I drilled my roof for NMO, I pondered 1/2 wave antenna, mounted on fabricated mount that would go under the bolts that hold the hinge of the rear hatch on Durango 2014. Advantages: no need for groundplane, ok to be on the edge of the roof (it's 1/2 wave), no roof drilling. Disadvantages: longer than 1/4 wave antenna. I went with drilled through the roof NMO, but I had something as big as your roof tent, I would consider again. You probably can fabricate something on the back, for the hinge mount, and it probably will be further from the tent (you need to open that hatch somehow, right?) than what's on your photo. Just a thought.

 

Also, in Taipei, the half of the cabbies carry the setup similar to what I just described. Prius or other hatchback with longish (for 70cm) antenna mounted with bracket that's attached under the bolts that hold the hutch strut. I tried to ask, but was met with the blank stare. I do not speak Mandarin, and cabbies probably do not know the details of the radio setup anyway.

[serrasalmus]

i can shift the tent forward and have room in the rear todo a nmo or move the mag mount to there. a concern i have with it in the back is, thats when trees are at there maximum hurt ur car value nad its unleashing it towards the rear of the vehicle?.

 

Before I drilled my roof for NMO, I pondered 1/2 wave antenna, mounted on fabricated mount that would go under the bolts that hold the hinge of the rear hatch on Durango 2014. Advantages: no need for groundplane, ok to be on the edge of the roof (it's 1/2 wave), no roof drilling. Disadvantages: longer than 1/4 wave antenna. I went with drilled through the roof NMO, but I had something as big as your roof tent, I would consider again. You probably can fabricate something on the back, for the hinge mount, and it probably will be further from the tent (you need to open that hatch somehow, right?) than what's on your photo. Just a thought.

 

Also, in Taipei, the half of the cabbies carry the setup similar to what I just described. Prius or other hatchback with longish (for 70cm) antenna mounted with bracket that's attached under the bolts that hold the hutch strut. I tried to ask, but was met with the blank stare. I do not speak Mandarin, and cabbies probably do not know the details of the radio setup anyway.

[OldRadioGuy]

The wavelength of GMRS is around 65cm which is like 25 inches while 11 meters is like 33 feet.

Shorter wavelengths do much better at getting through windows such as in a car. 

If you take a portable radio inside your car you'll probably get FM pretty well but not AM. 

GMRS is 1/4 the wavelength of FM so would do even better.

 

I think it's possible that you'll do just fine with the antenna on the hood.

There may be a couple angles that are a problem but mostly will do OK.

It's definitely worth a try.

 

We've used hand held radios between vehicles with my in the Sprinter van up front.

It has only one small window in the back which is a horrible scenario.

It's a huge metal box with almost no opening towards the back which was the direction to the other vehicle.

But it worked OK out to about a 1/2 mile.  It almost shouldn't have worked at all.

You could hardly imagine a worse situation but it wasn't that bad. 

 

So 460MHz is pretty good at sneaking through small openings.

 

Vince

 

Vince